Process for the production of ferromagnetic pure or isotype manganate mixed phases crystallizing in the ilmenite lattice

ABSTRACT

PRODUCTION OF FERROMAGNETIC PURE AND ISOTYPE MANGANATE MIXED PHASES OF THE COMPOSITION   NI1-XCOX.0.91-1.1MNO3; WHERE 0$X$0.20 THAT CRYSTALLIZE IN THE ILMENITE LATTICE, BY PRECIPITATING SUCH MIXED PHASE CONSTITUENTS FROM AN AQUEOUS SALT SOLUTION OF MANGANESE AND NICKEL, OR MANGANESE, NICKEL AND COBALT, IONS, IN QUANTIIATIVE PROPORTIONS WHICH CORRESPOND DIRECTLY TO THOSE OF THE REQUIRED END COMPOUND, BY INSTANTLY INTERMIXING SUCH REACTANTS WITH A BASIC PRECIPITANT AT ABOUT 0-100*C. OXIDIZING THE RESULTING SUSPENSION, AND THEN FILTERING, WASHING, CALCINING AND COOLING THE RESULTING PRECIPITATE.

F. HUND MANGANATE MIXED PHASE-S CRYSTALLIZING IN THE ILMENITE LATTICEFiled Aug. 28, 1968 PROCESS FOR THE PRODUCTION OF FERROMAGNETIC PURE ORISOTYPE May 18, 1971 FRANZ United States Patent 3,579,452 PROCESS FORTHE PRODUCTION OF FERROMAG- NETIC PURE 0R ISOTYPE MANGANATE MIXED PHASESCRYSTALLIZING IN THE ILMENITE LATTICE Franz Hund, Krefeld-Bockum,Germany, assignor to Farbenfabriken Bayer Aktiengesellschaft,Leverkusen, Germany Filed Aug. 28, 1968, Ser. No. 755,937 'Claimspriority, application Germany, Sept. 1, 1967, F 53,389 Int. Cl. C01g45/12 U.S. Cl. 252-62.51 9 Claims ABSTRACT OF THE DISCLOSURE Productionof ferromagnetic pure and isotype manganate mixed phases of thecomposition Ni Co -0.91-1.1 Mno,;

where 0x020 that crystallize in the ilmenite lattice, by precipitatingsuch mixed phase constituens from an aqueous salt solution of manganeseand nickel, or manganese, nickel and cobalt, ions, in quantitativeproportions which correspond directly to those of the required endcompound, by instantly intermixing such reactants with a basicprecipitant at about 0100 C., oxidizing the resllting suspension, andthen filtering, washing, calcining and cooling the resultingprecipitate.

This invention relates to the production of pure or isotype manganatemixed phases of the composition: Ni Co -0.91l.1 MnO where 0x0.20, whichcrystallize in the ilmenite lattice.

In recent years, ferromagnetic oxides have been used in a number ofdifferent fields, in particular for magnetic impulse recording. Thesenew ferromagnetic oxides also include the individual compounds of NiMnOwhich crystallize in the ilmenite lattice and their isotype mixed phasesNi Co MnO where x=from 0.01 to 0.99, which form a continuous series ofsolid solutions.

These ferromagnetic materials are produced, for ex ample, by heating amixture of manganese dioxide and the simple oxides of nickel and/orcobalt in an aqueous medium to temperatures above 500 C. under pressuresin excess of 500 atmopheres, and preferably between 1000 and 5000atmospheres (U. S. patent specifications Nos. 2,770,523 and 2,996,457).In addition, U.S. patent specification No. 3,039,964 describes thepreparation of ferromagnetic, crystalline complex oxides of manganeseand at least one of the oxides of nickel or cobalt showing the structureof an ilmenite crystal. In this process, a mixture of manganese oxidewith at least one of the oxides of nickel or cobalt is heated to between500 and 800 C. at elevated oxygen pressure in the presence of at least2% by weight of an inorganic fiuxing agent which is molten at thereaction temperature. The fiuxing agent may consist of boric acid, boronoxide, alkali metal hydroxides or alkali metal, silver, barium oraluminum fluorides, chlorides, sulfates, bisulfates, pyrosulfates,persulfates, perborates, tetraborates, nitrates or tungstates ormixtures thereof. The overall pressure prevailing in the system shouldnot exceed more than about 500 atmospheres.

U.S. patent specification No. 3,039,965 relates to a process forproducing the ferromagnetic crystalline complex oxides of manganese ofilmenite structure which are mentioned in U.S. patent specification No.3,039,964, in which a mixture of manganese salts, for example potassiumpermanganate, manganese nitrate, oxalate, halide or carbonate and atleast one nickel or cobalt salt, for exice ample nitrates, oxalates,halides and carbonates, with an atomic ratio of Mn to the other metalsin the range of from 1:1 to 2:1, is heated to a temperature in the rangeof from 450 C. to 800 C. under less than 500 atmospheres pressure.

French patent specification No. 1,421,055 relates to the preparation offerromagnetic NiMnO crystallizing in the ilmenite lattice. A mixture ofmanganese and nickel oxalates is precipitated with vigorous stirring atboiling point from an aqueous solution of manganese and nickel salts.After filtering, washing and drying, the precipitate is heated to atemperature of from 600 C. to 780 C. Due to the fact that the solubilityof the nickel and manganese oxalate differs for each precipitationtemperature, a calibration factor is required for the Mn +:Ni ratio inthe aqueous solution in order to adjust the desired MnzNi ratio in theferromagnetic end product for each precipitation temperature.

The processes described above have a number of disadvantages becauseeither high pressures are necessary or alternatively the reactions haveto be carried out in the presence of corrosive agents. Although the lastof these processes avoids these disadvantages, it has the drawback thatthe process conditions need considerable control.

A technically very simple process for the production of ferromagneticpure or isotype manganate mixed phases of the composition Ni Co MnOwhere 0x0.20, which can be carried out at atmospheric pressure in anoxygen-containing atmosphere, has now been found, in which an aqueoussolution containing manganese, nickel and optionally cobalt ions, whosequantitative proportions correspond directly to those of the requiredend compound, is precipitated with a basic precipitant, preferably withintensive stirring, at a temperature in the range of from 0 C. to C.,the resulting suspension is oxidized with an oxidizing gas, e.g. air,the precipitate is filtered off, washed and, after optional predrying,is calcined at a temperature of up to 800 C. in oxygen or anoxygencontaining atmosphere and is then slowly cooled.

X-ray photographs show that the black-coloured products thus obtainedhave a pure ilmenite lattice whose lattice constants in A. varyregularly in dependence upon the Co content.

The manganese, nickel and/or cobalt is used in the form of any of thecorresponding water-soluble salts. Although it is preferred to use thechlorides, it is also possible to employ the nitrates and/or sulfates.Suitable basic precipitants include aqueous solutions of alkali metalhydroxides such as sodium hydroxide, potassium hydroxide, ammoniasolutions etc. and aqueous suspensions of the alkaline earth metals,namely, hydroxides of magnesium, calcium, strontium or barium. It isalso possible to use gaseous ammonia. Precipitation should be carriedout from solutions of the highest possible concentration. The bases areadded in a quantity of from 70 to 130% of the stoichiometricallynecessary amount. A degree of precipitation of from 80% to is preferred.Optimal magnetic values are obtained in cases where precipitation iscarried out as quickly as possible, i.e. in seconds or a few minutes,i.e. at most 15-20 minutes, depending upon the quantities used.Precipitation may also be carried out by combining streams of the metalsalt solution and the precipitant in the precipitation vessel itself.Precipitation is preferably carried out at low temperatures, i.e. attemperatures of from 10 C. to 30 C. After precipitation the suspensionis oxidized with an oxidizing gas, preferably by introducing into thesuspension a finely divided stream of air, oxygen enriched air or evenoxygen for a time suflicient to have all the manganese ions present inthe suspension in the manganate i.e. Mn(IV)-form.

Temperatures of 820 C. should not be exceeded in the calcination of themanganate mixed phases. It is advantageous to carry out calcination instages, optionally with intermediate grinding. For this purpose, theproducts are heated to about 300 to 800 C., e.g. initially heated to atemperature of from about 300 C. to 600 C. and then to a temperatureabove 700 C., e.g. 720-7 80 C., the optimum temperature being about 740C. Calcination times of from about 30 minutes to approximately 2 hoursare usually suflicient.

Calcination can be carried out in one step i.e. by heating slowly thepreferably predried precipitate into a temperature of about 740 C., thewhole step being finished at a time of about one half to three hours.Preferably, however, calcination is performed stepwise in two to threesteps at a temperature of about 300 to 600 C. first and thereafter atabout 700 to 800 C. Optionally, the first temperature range is dividedin two ranges: in this case the precipitate is at first maintained forat least 10 minutes at a temperature of about 300 to 400 (3., thereafterfor the same time at about 500 to 600 C. and finally at about 700 to 800C. Each step is performed under oxidizing conditions at equal ordifferent periods of time i.e. for 10 minutes to 1 hour. After the lastcalcination the calcine is either cooled rapidly in l to 3 seconds, e.g.by chilling with water or cool air or cooled slowly in about 2 to 5hours, i.e. without any additional precautions, whereby slow cooling isto be preferred in order to achieve products with optimum magneticproperties.

The process is extremely easy to carry out on a commercial scale.Precipitation vessels in glass, ceramics or acid-resistant steel, andenamelled or rubberised iron containers, equipped with a stirringmechanism are required in which an air and/or ammonia gas distributor isinstalled and which may receive the precipitation solution or suspensionfrom a feed pipe. Filtration, washing, drying, calcination and grindingmay be carried out either continuously or at intervals in simpleconventional apparatus.

After they have been ground and dispersed, the resulting ferromagneticpure or isotype manganate mixed phases Ni Co MnO where x020crystallizing in the ilmenite lattice may be applied in a suitable layerthickness, for example to an organic layer support in a suitablevehicle, similar to -Fe O or CrO and may be used for magneticallyrecording sound, pictures and impulses. By virtue of the particularlylow Curie temperature of about 160 C. for pure NiMnO which is reducedeven further with increasing incorporation of CoMnO in solid solutioninto the NiMnO- (pure CoMnO having a Curie temperature of about 118 C.),the ferromagnetic, pure or isotype manganate mixed phases Ni Co MnOwhere 0x0.20, crystallizing in the ilmenite lattice, may be used inother fields, as suggested above all by the characteristics remanencetemperature dependence of the preparations. In the figure of thedrawing,measured Br/5-values are plotted against temperature for preparation 6.2of Example 6 and Table 6. Curve A shows values measured in a heatedsolenoid, whilst curve B shows values after cooling to 23 C. After thespecimen had been heated to the measuring temperature, it was fullymagnetized with a field of 1500 oersted and the remanence was measuredafter the energizing field had been cut out both at the measuringtemperature indicated and after cooling to 23 0., without the energizingfield being switched on again in the meanwhile. The remanence values inthe heated solenoid show the high increase in temperature expected andthe disappearance of the values at the Curie temperature which in thiscase measures about 158 C. After cooling to 23 C., the

remanence shows an almost rectangular trend. Up to 135 C., the remanenceincreases with increasing preheating temperature and then from 140 C.falls almost vertically to zero on reaching the Curie preheatingtemperature.

Finely divided ferromagnetic substances such as those produced inaccordance with the present invention, with low Curie temperatures andapproximately rectangular Br/fi-temperature curves after cooling arerequired, in particular for magnetic copying and duplicating processesof the kind described in US. patent specification No. 2,793,135. Anoriginal with areas that allow infra-red light through at difi'erentintensities, for example, in the formof drawings, letters and so on, iscopied through a beam of infra-red light onto a base plate in which theaforementioned ferromagnetic material is present in fine distribution inthe magnetized state. Under the areas that are permeable to light, thebase plate is heated to beyond the Curie temperature, eliminating theferromagnetism at these areas. Those areas that are not afiected by thelight are not heated and remain ferromagnetic. The latent magnetic imageof the base plate can be made visible with a ferromagnetic toner powder,for example, after a sheet of white paper has been laid over it, andpreserved in the usual way. By virtue of the inevitable lateraldiffusions of heat during exposure of the base plate to infra-red light,a ferromagnetic with the aforementioned rectangular Br/a-temperaturecurve finely dispersed in the base plate provides a high contrast ratioamong the light-dark particles of the original to be copied and hencemakes even small letters easy to read. The ferromagnetic base plate forthe copying and duplicating process may also contain the ferromagneticmaterial present in fine dispersion in the unmagnetized state.Magnetisation may be carried out during exposure. The areas affected bythe infra-red light which are heated to beyond the Curie temperature arenot magnetized by the energizing field. The latent magnetic image isagain made visible as described above.

The relationship 0x020 means that x is zero or less than or at mostequal to 0.20. Also, the atomic ratio of MnzNi or Mn:(Ni+Co) may heexpressed as 1.00- 1.10:l.10-1.00 or 0.91-1.11.

The invention is further illustrated, without limitation, by thefollowing examples and tables, wherein the designation means one-halfmolar solution of the particular salt or cation and means one molarsolution thereof. Slow cooling means cooling of the calcine withoutadditional precautions, i.e. in a time of about 1 to 5 hours, dependingon the quantity of the product. Quick cooling is eflected by chillingthe calcine with water.

EXAMPLE 1 The test conditions and results for normal (starting with 500and 1000 ml. of a Q 2+ 1 2 Mn and 2 N1 salt solution) and inverse(starting with 500 and 1000 ml. of a ZmNaOH-solution) precipitation,with the precipitant added in a single batch, i.e. pouring, or with thesecond component added dropwise over a period of from 15 to 20 minutes,are set out in Table 1. After the mixed hydroxides had been precipitated(i.e. at 20 C.) with intensive stirring, the precipitate was oxidized bybubbling air therethrough for 10 minutes, then filtered off, washed,predried at C. and, after powdering in each case, was calcined byheating in three stages to the maximum temperature specified of 740 C.in the presence of air, i.e. for 30 minutes at temperature of(400+600+740 C.). Both in normal and in inverse precipitation, the bestmagnetic data are obtained in cases where the mixed hydroxides areprecipitated in a single batch, i.e. by pouring.

EXAMPLE 2 Table 2 shows the results of tests in which the precipitationtemperature was varied under otherwise the same optimal precipitationconditions mentioned in Example 1 (starting with the metal salt solutionand precipitating in one batch). A precipitation temperature of around20 C. gives optimal magnetic data.

EXAMPLE 3 Table 3 contains the magnetic data of tests in which thedegree of precipitation of the salt solution was systematically variedunder the aforementioned efiective working conditions, otherwise usingthe same type of conditions as mentioned in Example 1. At lowprecipitation levels (100 to 80% of the theoretical), the magneticproperties vary less noticeably than in cases where the theoreticalprecipitation level of 100% is exceeded in favour of significantlyhigher values. Ca1- cination was performed as described in Example 1.

EXAMPLE 4 Table 4 shows the test conditions and results for theoreticalprecipitation of a 1000 ml.

salt solution by 1000 ml. of 2m NaOH at room temperature in a singlebatch with stirring for 8 minutes, otherwise following the procedure ofExample 1. The anions of the metal (II) salt solution were varied. Thebest magnetic data were obtained from the chloride solution, the worstfrom the sulfate sodium, although all anions were efl'ective.Calcination was performed as described in Example l.

Mn and? Ni EXAMPLE 5 In this case, the basic precipitant was varied at100% theoretical precipitation level for metal (II) chloride solutions,otherwise following the procedure of Example 1. The test conditions andresults are set out in Table 5. Judging from the magnetic valuesobtained. NaOH and Ca(OH) are the best precipitant, although all wereeffective. Calcination was performed as described in Example 1.

EXAMPLE 6 In this example, whose conditions and results are set out inTable 6, otherwise following the procedure of Example 1, the influenceof the calcination temperature upon the mametic values was investigatedfor deposits precipitated and worked up under standard conditions. X-raytests show that an ilmenite lattice is present up to 780 C., whilst, ata calcination temperature of 820 0, both the ilmenite lattice and themagnetism disappear. The choice of the calcination temperature isgoverned by the mag netic values required, although calcinationtemperatures above 800 C. irreversibly destroy the magnetic ilmenitephase.

EXAMPLE 7 Table 7 shows results for normally prepared precipi tates,following the procedure of Example 1, which precipitation were quicklyheated for 30 minutes at 740 C. either directly or through intermediatestages comprising calcination for 30 minutes at 400 C. and 600 C. Thespecimens calcined at 740 C. through intermediate stages were alsocooled quickly or slowly from the final calcination temperature. Themethod comprising precalcination for 30 minutes at 400 C. and 600 C. andslow cooling from the final calcination temperature of 740 C. providedthe best magnetic data.

EXAMPLE 8 Table 8 reports tests and their results in which ferromagneticmixed phases of the general composition of ilmenite structure(x=0.000.50) were prepared fol lowing the procedure of Example 1. Thecombined manganese (II), nickel (II) and optionally cobalt (II) chloridesolutions with a total volume of 500 ml. were precipitated in one batchwith vigorous stirring with 500 ml. of 2m NaOH at room temperature (8minutes), the precipitate Was oxidized by bubbling air therethrough for15 minutes, then filtered off, washed, dried at 120 C. and, afterpo'wdering, calcined for 90 minutes at equal intervals to a temperatureup to 740 C., i.e. for 30 minutes at 400, 600 and 740 C. and cooledslowly from the final calcination temperature. With up to about 20 molpercent incorporation of CoMnO into NiMnO both the ferromagnetism andthe ilmenite lattice of the isotype mixed phase remain intact. Withincreasing incorporation of CoMnO in the NiMnO the coercive forceincreases whilst the remanence decreases.

The ferromagnetic pure compounds crystallizing in the ilmenite latticeof NiMnO or of the mixed phases Ni Co MnO where 0x0.20, obtained inaccordance with the examples, may be used in a variety of fields wheremagnetic oxides are used, for example for magnetic pulse recording ontapes and as magnetic core materials for coils.

TABLE 1.MAGNETIC DATA IN DEPENDENCE UPON THE TYPE AND SPEED OFPRECIPITATION Calcination at 740 C.

500 ml. of starting solution 500 ml. of precipitation Type of (1,000 ml.of starting solution (1,000 ml. of preeipi- Ty e of solution)precipitation solution) tation coo ing Br/fi 1H,,

Test number:

1.1 2/m MnClZ plus 2/m NiCl 2 m NaOH (500 m1.) Pouring Slow 93 368 1.2Same as above Same as above 15 minutes do 49 68 1.3 2 m NaOH (1,000 ml.)2/m M11012 plus 2/m NiCl Pouring do 104 345 1.4 Same as above Same asabove 20 minutes. -d0. 87 233 1:5. 2/m IVIllClz plus 2/m NiCl 2 m NaOH(1,000 m1.) Pouring do 98 420 TABLE 2.MAGNETIC DATA IN DEPENDENCE UPONTHE PRECIPITATION TEMPERATURE Ptreteipi- Calcination at 740 C.

a ion 1,000 ml. of starting solution 1,000 ml. of precipitant tempera-Type of (2,000 mi. of starting solution) (2,000 ml. of precipitant) tureC.) cooling Br/6 H, Test number" 9 1 2/m MnCl; plus 2/m NiCl 2 m NaOH(1,000 ml.) 10 Slow 90 322 Same as above .do 20 do 98 420 20 lo 97 39620 Qui ck 99 453 do 92 287 1 1,011 ml. llm N i01 plus 989 m1. l/m MnCl-solution=2,000 ml. of 1/m metal (II) chloride solution.

TABLE 3.MAGNETIC DATA IN DEPENDENCE UPON THE DEGREE OF PRECIPITATION OFTHE METAL (II) CHLORIDE SOLUTION Percent pre- Calcination at 740 C.

cipitation 500 1111. 01 of theo- Type of 500 1111. of starting solutionprecipitant reticel cooling Br/6 H.

Test number:

3.1 2/111 M11011 plus 2/111 NiCiz. 1.60 m NaOH-.. 80 Slow.... 73 366Same as above. 1.80 In NeOH 90 do 93 313 1.90 In NeOH. 95 do 01 460 2.00m NaOH. 100 do 93 368 2.10 m NeOH 105 do 96 334 2.20m NaOH 110 do. 88211 3.7 ..do 2.30 111 NaOH..- 115 .do 87 141 TABLE 4.MAGNETIC DATA INDEPENDENCE UPON THE ANION OF THE METAL (II) SALT SOLUTION Anion ofCelcination at 740 C.

the metal 1,000 1111. of starting 1,000 mi. of (II) salt Type ofsolution precipitant solution cooling Br/6 H Test number:

4.1 2/111 Mn plus 2/m Ni -i0ns. 2 m Na0H 201 Slow. 98 420 4.2 Same asabove Same SO4 do 37 103 4.3 do do 2NO3 .d0. 86 153 TABLE 5.MAGNETICDATA IN DEPENDENCE UPON THE PREOIPITANT Calcination at 740 0.

2,000 1111. of starting solution 2,000 ml. of precipitant Type of (1,000mi. of starting solution) (1,000 mi. of precipitant) cooling Br/fi 1H0Test number:

5.1 2/111 MnCh plus 2/111 NiCli 2 n e 99 453 5.2 Same as above 2 nCa(OH) (1,000 1111.). 3 403 5.3 .-do 1 11 NaOH plus 1 11 No.10, 1 96 2801,000 1111.). 5.4 do. 2nNH4OH (1,0001nl.) Quick 71 288 5.5 0.3 1n M11011plus 2/111 NiCh (1,000 0.2 m @1104 plus 1.4 m Slow.... 76 81 1111.).NaOH (1,000 1111.).

1 Precipitation incomplete.

TABLE 6.MAGNETIC DATA IN DEPENDENCE UPON THE CALCINATION TEMPERATUREType of calcination (40.12.11.1 1... new Br/fi H, B116 1H, Br/fi H, B116H.

Test number 6.1. 93 539 99 453 56 408 0 0 Type of oalcination 30 minutes+30 minutes +30 minutes +30 minutes +30 minutes (400+fi00+700 O.) at 720C. 740 0. 760 0. 780 C.

Br/& 1151., 131/6 H. Brlfi 1H. Br/a H1, 131/6 121.,

Test number 6.2 81 178 90 231 97 250 105 243 48 277 NOTE:

6.1=1,011 m1. of 1 1n NiChand 989 m1. of 1 n1 MnCli-solution are mixedand precipitated by pouring with 2,000 1111. of 2 m NaOH at 20 0., 8minutes stirring.

6.2=400 ml. (2/111 M11011 plus 2/111 NiCh) are precipitated in one pourwith 400 1111. of 2 n1 NaOH at C. "20 and stirred for 8 minutes.

TABLE 7.MAGNETIC DATA IN DEPENAJTEI Xg EOUPON THE CALCINATION CONDITIONSIPrecipitant, 1,000 1111. of 2 m NaOH] 30 minutes 30 minutes 1,000 ml.of Quick heating (400+600+740 C.) (400+600+740 C.) starting solution to740 0. quick cooling slow cooling ml. 1 m 1111. 1 1n MnClr NiChsolutionsolution Br/fi H1, Br/6 1H, 131/5 JHu Test number:

TABLE 8 [Magnetic data in dependence upon the composition of the NLlCoxMnoi-mixed phases] Starting solutions: m1. 1 m

solutions o Caicination at 740 C.

X in Type of NiiqCmMno MnCl NlCI: C0011 cooling Br/a H Test number:

0 00 250 250 SloW 93 368 0. 02 250 245 5 96 387 0 04 250 240 89 420 0 06250 235 74 437 0. 08 250 230 70 483 0. 10 250 225 70 471 0. 20 250 20038 544 9 What is claimed is: 1. Process for the production offerromagnetic pure and isotype manganate mixed phases of the compositionwhere Ox020 that crystallize in the ilmenite lattice which comprisesprecipitating said mixed phase constituents from an aqueous metal saltsolution containing as reactants correspondingly manganese ions and amember selected from the group cosisting of nickel ions, and mixtures ofnickel and cobalt ions, in quantitative proportions which corresponddirectly to those of the required end compound by reacting saidreactants at a temperature of between about to 100 C., with a basicprecipitant selected from the group consisting of aqueous solutions ofalkali metal hydroxides and ammonia, aqueous suspensions of alkalineearth metal hydroxides, and mixtures thereof, oxidizing the resultingprecipitate that is suspended in said solution with an oxygen-containinggas to convert all the manganese to the tetravalent state, filtering offthe precipitate in said suspension and washing the precipitate,calcining the precipitate at a calcining temperature of from about 300C. up to 800 C., the final calcining temperature being at least about700 C., in an oxygen-containing atmosphere and then slowly cooling thecalcined material.

2. Process according to claim 1 wherein the reacting of said reactantswith said basic precipitant is efiected with intensive stirring.

3. Process according to claim 1 wherein the precipitation is carried outat a temperature of between about to 30 C.

4. Process according to claim 3 wherein the precipitation of the metalsalt solution is effected with about 70 to 130% of the correspondingstoichiometric amount of the basic precipitant.

5. Process according to claim 4 wherein a solution of the correspondingchlorides is used as the metal salt solution.

6. Process according to claim 1 wherein said calcination is carried outin a plurality of stages, at a temperature that increases from stage tostage from about 300 C. up to at most 800 C.

7. Process according to claim 6 wherein said filtered and washedprecipitate is pre-dried prior to calcining.

8. Process according to claim 6 wherein said calcination is carried outin three separate stages at 300 to 400, 500 to 600 and 700 to 800 C.,respectively, and upon slow cooling after the last stage the resultingcalcined material is reduced to powder form.

9. Process according to claim 1 wherein said aqueous salt solution ofsaid ions is that of a salt selected from the group consisting ofchloride, nitrate, sulfate, and mixtures thereof, wherein said basicprecipitant is selected from the group consisting of correspondingsolutions of sodium hydroxide, potassium hydroxide, and ammonia, andsuspensions of magnesium hydroxide, calcium hydroxide, strontiumhydroxide, and barium hydroxide, and

mixtures thereof, and wherein the precipitation is carried out at atemperature of between about 10 to 30 C., and the precipitation of themetal salt solution is elfected with about to of the correspondingstoichiometric amount of basic precipitant.

References Cited TOBIAS E. LEVOW, Primary Examiner J. COOPER, AssistantExaminer US. Cl. X.R. 2358

